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1 Polish Journal of Ecology

1 2004

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Human impact on the ecosystem of lake Ruusmae (southern Estonia) traced in the sediments

Punning J.-M., Koff T., Sakson M., Terasmaa J.

Polish Journal of Ecology

2004

Vol. 52, nr 3

285-299

Long-term limnological monitoring data (from 1971 to 2001) and the documented human load history were compared with sediment core record in a small lake Ruusmae in southern Estonia. It was established that pollen data reflect the main land-use changes on the catchment rather adequately. The response of other palaeoecological indicators (fossil pigments, carbon and nitrogen, phosphorous) and diatom composition to the changes in the nutrient input from the nearby large cattle-breeding centre took some time. When the load had exceeded certain limit, the transition of the lake from eutrophic to hypertrophic state took place very quickly. Simultaneously with the reorganisation of matter cycling rapid changes occured in the diatom community, in which species characteristic of hypertrophic lakes became dominant. Irrespective of the drastic drop in the external load at the beginning of the 1990s the changes in the biogeochemical matter cycling and diatom community are modest.